On the nature of cosmic ray spectrum hardening at 230 GV

The high-accuracy measurements of protons and nuclei energy spectra in the cosmic ray experiment AMS-02 confirmed the earlier experimental results of ATIC-2, CREAM and PAMELA measurements on the presence of spectral hardening at magnetic rigidity about 230 GV. The AMS-02 data on the secondary nuclei Li, Be and B indicated that the hardening is most probably due to the transition to weaker rigidity dependence of cosmic ray confinement time in the Galaxy above 230 GV. However, the possible hardening of the source spectrum is also not excluded. To study the origin of spectrum hardening, we use the numerical code GALPROP to compute the propagation of cosmic rays under different assumptions on the rigidity dependence of cosmic ray source and propagation parameters in a few Galactic models.